Non-local correlations and quasiparticle interactions in the Anderson model

A comparative study of real many-body dynamics of single-impurity, two-impurity and periodic Anderson models (SIAM, TIAM, PAM) is performed using a recently developed irreducible Green's function method. A detailed analysis of the correct definitions of the generalized mean field corrections is given for both weak and strong Coulomb correlations. We find that for the strongly correlated regime the mean field renormalizations are described by complicated correlations which do not reduce to the functional of mean densities of electrons. The approach we suggest permits to calculate in a self-consistent way the damping of quasiparticles in both considered limits, i.e. weak and strong correlations. Also this approach gives a complete and compact description of many-body dynamics for the considered system. The corresponding spectrum consists of a broad continuous spectrum and a few localized levels embedded in the continuum. Finally we point out the implications of our results for the problem of interplay between single-site Kondo screening and interimpurity RKKY interaction.